Your question has an assumption that is not correct; "If the Almighty God began life as a man." Not anywhere in Mormon Doctrine (Canonized Scripture) does it say that God began life as a non-divine man. In fact there are many scriptures that state that God is eternal and has always been God.
The statement that "As man is God once was, and as God is man may become." Does not state that God, when He was a man was not divine and was not still God. Jesus Christ is God, and He was once a man and still is a man, but was always divine and the Son of God.
As man is Christ once was, and as Christ is man may become.
Philippians 3:21; "Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself." The resurrected righteous shall have a glorious body even like Christ body.
Revelation 21:7; "He that overcometh shall inherit all things; and I will be his God, and he shall be my son." If we overcome evil we can inherit all things that the Father hath.
1 Peter 5:6; "Humble yourselves therefore under the mighty hand of God, that he may exalt you in due time:" What else does it mean to be exalted, other than becoming a glorified Son of God?
2 Peter 1:3-4; "According as his divine power hath given unto us all things that pertain unto life and godliness, through the knowledge of him that hath called us to glory and virtue: Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust." The righteous shall be given godliness and are partakers of the divine nature, and if divine, then they are gods and Lords, so one can understand that Christ is the God of gods and Lord of Lords, not a God of evil gods or evil Lords. Revelation 19:16, Deuteronomy 10:17.
Revelation 3:21; "To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne." If we are joint-heirs with Christ and inherit all things that the Father has, becoming partakers of the divine nature and obtain the glory of our Lord and sit down with Christ in His throne and become one with God, what does that say about the righteous heirs. Those that share all things, Glory, Knowledge, Power and divine nature with the Father are worthy of, according to the word of God, the title “God.”